Complex coils having fibered centers

ABSTRACT

A vasoocclusive device in the form of a coil for placement in the vasculature of an animal to form thrombus in a selected site such as an aneurysm or AVM. The device involves a primary coil form having thrombogenic fibers placed on the coil in a specified fashion. The coil will pass through the lumen of a vascular catheter in the primary coil form and evolve into a convoluted or complex secondary form when ejected from the catheter&#39;s distal end. The fibers are attached to the coil and cooperate with the coil so that upon ejection from the catheter, the convoluted coil forms a shape in which the central region or secondary coil form center that contains the majority of these fibers.

RELATED APPLICATIONS

This is a continuation of U.S. Ser. No. 08/540,354 filed Sep. 29, 1995,now U.S. Pat. No. 5,700,258 to Mirigian et al., filed Sep. 29, 1995,which is a continuation-in-part of U.S. Ser. No. 08/265,188, now U.S.Pat. No. 5,549,624, issued Aug. 27, 1996, to Mirigian and Van, filedJun. 24, 1994, the entirety of which is incorporated by reference.

FIELD OF THE INVENTION

This invention is a vasoocclusive device. It is a helically wound coilplaced in the vasculature of an animal to form thrombus in a selectedsite such as an aneurysm or AVM. The device involves a primary coil formhaving thrombogenic fibers placed on the coil in a specified fashion.The coil will pass through the lumen of a vascular catheter in theprimary coil form and evolve into a convoluted or complex secondary formwhen ejected from the catheter's distal end. The fibers are attached tothe coil and cooperate with the coil so that upon ejection from thecatheter, the convoluted coil forms a shape in which the central regionor secondary coil form center that contains the majority of thesefibers.

BACKGROUND OF THE INVENTION

Vasoocclusive devices are surgical implants placed within blood vesselsor vascular cavities, typically by the use of a catheter, to form athrombus and occlude the site. For instance, treatment of a stroke orother such vascular accident may include the placement of avasoocclusive device proximal of the site to block the flow of blood tothe site and alleviate the leakage. An aneurysm may similarly be treatedby introduction of a vasoocclusive device through the neck of theaneurysm. The thrombogenic properties of the vasoocclusive device causesa mass to form in the aneurysm and alleviates the potential for growthof the aneurysm and its subsequent rupture. Other diseases, such astumors, may often be treated by occluding the blood flow to the tumor.

There are a variety of vasoocclusive devices suitable for formingthrombus. One such device is found in U.S. Pat. No. 4,994,069, toRitchart et al., the entirety of which is incorporated by reference.That patent describes a vasoocclusive coil that assumes a linear helicalconfiguration when stretched and a folded convoluted configuration whenrelaxed. The stretched configuration is used in placement of the coil atthe desired site and the convoluted configuration occurs when the coilis ejected from the catheter and the coil relaxes.

There have been increasing needs to increase the inherentthrombogenicity of these devices. One way of increasing thatthrombogenicity is to increase the amount of fiber found in the device.U.S. Pat. No. 5,226,911, to Chee et al., describes a vasoocclusive coilwith attached fibrous elements. The fibers are looped in a generallyserpentine manner along the coil. The fibrous loops are affixed to (orlooped through) the coil at spaced intervals along the coil. The use ofmultiple fibrous windings is noted in the patent but that use is said toinvolve placement of the fibers 180° apart on the circumference of thecoil.

It should be noted that additional filaments on the exterior of the coilincrease the friction of the fibrous coil against the catheter lumen.Added filaments increase the desired thrombogenicity. It is this balancewhich is difficult to make. We have found a way to increase the overallthrombogenicity without substantially affecting the friction of theinventive coil against the deployment catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial side view of a typical coil (expanded) madeaccording to the invention.

FIG. 2 shows a partial side view of the inventive coil showing detailsof fiber attachment.

FIG. 3 shows a partial side view schematically depicting the attachmentof multiple filamentary elements.

FIG. 4 shows a cross section, end view of the inventive coil showingplacement of the filamentary elements.

FIGS. 5A and 5B are fragmentary cross-sections of end sections of theinventive fibered coils.

FIG. 6 shows a plan view of the relaxed inventive coil after deployment.

FIGS. 7, 8, and 9 show respectively end and side view of a primary formof a variation of the invention and the end view of the secondary formof that inventive coil.

FIG. 10 shows the side view of the primary form of a tufted variation ofthe invention.

FIGS. 11 and 12 show respectively end and side views of the FIG. 10coil.

DESCRIPTION OF THE INVENTION

As has been noted above, this invention is a vasoocclusive device and,in particular, it is a fibered coil having a complex shape and amajority of the fibers located on the interior of the complex shape.There are three variations of the general concept of this devicedescribed below. The first variation is a coil in which the attachedfibers are comparatively lengthy and are looped along the primary formof the coil so that when the coil assumes its secondary or complex form,the fibers reside mainly in the center region of the complex. A secondvariation involves a coil in which the attached fibers are tufts and aresituated so that the resulting complex coil includes a center region ofthe complex coil. The third variation is a coil in which a portion ofthe axial length of the primary coil includes fibers. The complex formof the coil is designed so that the portion of the coil having fibersevolves into a position which is located centrally within the complexcoil center.

The first variation noted above is discussed with regard to FIGS. 1-6.FIG. 1 shows a length of the fibered coil (100). It is made of severalcomponents: a helical coil (102), a first fibrous element (104), and asecond fibrous element (106). The end of the coil may be sealed to forma cap (108).

The helical coil (102) is typically of a radiopaque material such astungsten, tantalum, gold platinum, and alloys of those materials.Stainless steels are also suitable. The use of various polymers, such aspolyethylene, polyurethane, and the like as the coil material is alsocontemplated. The use of polymeric materials typically involves the useof known radiopaque fillers such as powdered tantalum, powderedtungsten, barium sulfate, bismuth oxide, bismuth carbonate, or the like.Preferred, however, is an alloy of platinum with a minor amount oftungsten. This alloy is very flexible and yet the tungsten takes away ameasure of ductility from the resulting coil.

The coil may be from 0.2 to 100 cm in length or more. The diameter ofthe coil is from 0.004" to 0.015", typically from 0.008" to 0.012". Thewire making up the coil is 0.0005" to 0.002" in diameter. The coil maybe wound to have a tight pitch, that is to say, that there is no spacebetween the adjacent turns of the coil, or it may have some spacebetween adjacent turns. Most desirable, from the point of view of havinga high content of fiber, is a coil which is slightly stretched in themanner and in the amount described below.

The first (104) and second (106) fibrous elements typically are bundlesof individual fibers (5 to 100 fibers per bundle), but may be individualfibers. The fibers may be of a number of different thrombogenicmaterials. Suitable synthetic fibers include polyethylene terephthalate(e.g., DACRON), polyesters, especially polyamides (e.g., the Nylons),polyglycolic acid, polylactic acid, and the like. Other less desirablesynthetic polymers, because of their decreased thrombogenicity, includefluorocarbons (Teflon) and polyaramids (Kevlar). Natural fibers such assilk and cotton are also quite suitable.

The fibered coil (100) shown in FIG. 1 is in the general shape as foundin the catheter lumen. The coil (102) has been stretched to place thefirst fibrous element (104) and second fibrous element (106) close alongthe outer periphery of the coil (102). This stretching lessens theoverall diameter of the fiber coil (100) as seen by the catheter lumen.

As may be seen more clearly in FIG. 2, the multiple fiber elements arealternately looped along the coil. That is to say that the looping ofthe first fiber element (104) through coil (102) alternates with thelooping of the second fiber element (106) through coil (102). The fiberelements may be looped through the coil (102) as shown in FIGS. 1 and 2or they may be tied at intersections with the coil (106) although,because of the interference between the knot end catheter offered by theknot, a mere looping is preferred. The end passage of the fibers throughthe coil desirably involves a knot. Only a pair of fibrous elements (104and 106) are shown in FIGS. 1 and 2; multiple such fiber elements may beused, however. Additionally, it is quite desirable that the spacing ofthe fibrous elements as they cross the coil need not be equal.

As is portrayed in the side view found in FIG. 3, multiple filamentnumbers having a short coil spacing (110), an intermediate coil spacing(112), and a long coil spacing (114). These various fiber spacings tendto increase the randomness of the fibered center of the randomized coilafter it is released from the catheter. This benefit will be discussedin more detail below.

A significant aspect of this variation of the invention is shown in FIG.4. That drawing, a cross-section view, shows that the various fiberelements (in this example, 104 and 106) occupy a small radial sector ofthe coil's circumference. Although, upon deployment, the various fiberelements will shift toward each other to a modest degree, the filamentsmust be placed in the same 90° quadrant (105) to attain maximum benefitof the invention. This quadrant is measured perpendicularly to the axisof the stretched coil.

Finally, FIG. 1 shows an end (108) on coil (102). Such ends (108) aretypically produced by heating the end of the coil (102) to melt a smallsection of the coil and form a closed end (108). FIG. 5A shows aclose-up of the end (108) and the coil (102).

FIG. 5B shows an additional variation in which the coil (102)encompasses a control wire (116) and an end cap (118) having a holetherethrough. Use of such a control wire (116) allows "ganging" of thecoils or placement of a number of coils "nose-to-tail" within thecatheter and therefore gives the attending surgeon the choice of usingone or more coils without reloading the catheter.

FIG. 6 shows the shape of the coil (102) after it has been deployed fromthe catheter. The coil (102) encompasses an interior region (124) whichhas fiber passing through the region which is formed by creation of asecondary diameter (126). This region (124) of fibers provides foradditional thrombogenicity in the open region (124) among the secondarycoil (126) turns. This added and spaced fiber results in an enhancedthrombus formation rate--typically a matter of concern in using thesedevices for treatment of vascular problems. We have found that by use ofthis procedure of fiber attachment, upwards of 65% of the fibers foundon the coil are introduced into the open region (124), preferably morethan 75% and,most preferably, more than 85%.

The coils (102) discussed above are "preformed" so as to allow the coil(102) to assume the secondary diameter (126) shown in FIG. 6. The patentto Ritchart et al. (U.S. Pat. No. 4,994,069), discussed above, discussesa number of ways to preform such coils, e.g., by crimping the coil atvarious intervals. Another way to preform the coils, particularly whenusing the preferred platinum/tungsten alloy mentioned above is bywinding the coil on a mandrel into the secondary diameter shown in FIG.6 and then modestly heat-treating the thusly-wound coil. The coil willretain sufficient flexibility to extend, in a linear fashion, through acatheter lumen. Other complex coil forms having a central region mayalso be utilized in this invention.

A second variation of this invention is shown in FIGS. 7-9. Thematerials of construction, sizes, shapes for this variation are the sameor similar to those for the variation discussed above. This variation issimilar to the FIG. 1-6 variation except that the fibers (140) aremounted on the coil (142) in the form of tufts. The tufts of fiber (140)are again desirably mounted in a quadrant (144) viewed along the axis ofthe coil. The tufts (140) are shown in FIG. 8 as being merely insertedbetween the turns of the coil (142). The clearance between the variousturns of the coil will usually be sufficient to hold the fibers inplace. However, it is also desirable to deform the polymeric material ofthe fibers using a heat setting procedure such as is described in U.S.patent application Ser. No. 08/431,460, to Mariant et al, the entiretyof which is incorporated by reference.

The complex form of the coil (142) is shown in FIG. 9. The fibers (140)are shown within the central region (144) which is located away from theexterior of the complex coil shape.

FIGS. 10-12 show a variation (150) of the invention in which the fibers(152) are placed along some portion (154) of the primary axis of thecoil. The complex form of the coil assembly (150) is shown in two viewsin FIGS. 11 and 12. The coil is designed so that the portion (154) ofthe coil assembly (150) found in the interior of the relaxed complexform as shown in FIGS. 11 and 12, is interior to the coil assembly(150). The complex forms suitable for use in this invention are easilymade according to any of the disclosures described above; the stepsusually involving only winding the primary coil on a mandrel of suitableshape to form the secondary or complex shape and annealing at anappropriate temperature.

The variations of this device may be deployed in the same manner as arethe coils described in the Ritchart et al or Chee et al patentsdiscussed above. In general, a vascular catheter is introduced into thebloodstream at a convenient site, often the femoral artery in the groin,and advanced to the site of concern. As has been noted elsewhere, thesesites ore often in the cranial arteries but may be in any other sitewhere occlusion is desired. Guidewires are typically used to direct thecatheter to the desired site but blood flow is used to directflow-directed catheters. Once the distal end of the catheter is at thesite, the catheter lumen is cleared of guidewires and the like. Theinventive coil is then introduced into the lumen, often with the help ofa cannula to preserve the shape of the elongated coil until it entersthe catheter lumen. A pusher, typically similar in shape to a guidewireis then introduced into the catheter lumen to push the inventive coilalong the interior of the catheter and out its distal end. Once the coilis safely in place, the catheter is removed from the body.

This invention has been described using specific details to augment theexplanation of that invention. However, it is not our intent that thespecifics so used would be in any manner limiting to the claimedinvention. It is our intent that variations of the invention which wouldbe considered equivalent to one having ordinary skill in this art bewithin the scope of the claims which follow.

We claim as our invention:
 1. A vasoocclusive device comprising:(a) acoil having helical windings extending between a first end and a secondend, a primary coil axis extending between said first end and a secondend, and defining a primary coil form, said primary coil form beingself-forming into a selected secondary coil form with a secondary coilform interior, and (b) a plurality of fibrous elements attached to saidcoil and located with respect to said primary coil form so that uponsaid self-forming, the majority of said plurality of fibrous elementsresides within said secondary coil form interior.
 2. The vasoocclusivedevice of claim 1 wherein said plurality of fibrous elements arethreaded through the helical coil primary form in a quadrant measuredgenerally perpendicular to the primary coil axis.
 3. The vasoocclusivedevice of claim 1 wherein the material making up said plurality offibrous elements is selected from silk, cotton, polyethyleneterephthalate, polylactic acid, polyglycolic acid, polyesters,fluorocarbons, and polyaramids.
 4. The vasoocclusive device of claim 3wherein the fibrous elements are polyethylene terephthalate.
 5. Thevasooclusive device of claim 1 wherein the secondary coil form interiorcontains at least about 65% of the plurality of fibrous elements.
 6. Thevasooclusive device of claim 1 wherein the secondary coil form interiorcontains at least about 85% of the plurality of fibrous elements.
 7. Thevasoocclusive device of claim 1 wherein said plurality of fibrouselements comprises a multiplicity of fibrillar tufts extending radiallyfrom the primary coil axis.
 8. The vasoocclusive device of claim 7wherein the multiplicity of fibrillar tufts extending radially from theprimary coil axis are inserted around said helical windings.
 9. Thevasoocclusive device of claim 8 wherein the multiplicity of fibrillartufts extending radially from the primary coil axis are inserted aroundsaid helical windings in a quadrant measured generally perpendicular tothe coil axis.
 10. The vasoocclusive device of claim 1 wherein fibersare located along only a portion of the axis of the primary coil formand that portion of the primary coil form resides within said secondarycoil form interior upon said self-forming.